A book is a series of pages assembled for easy portability and reading, as well as the composition contained in it. The most common modern form of book is a codex volume consisting of rectangular paper pages bound on one side, with a heavier cover and spine, so that it can fan open for reading. Books have taken other forms, such as scrolls, leaves on a string, or strips tied together; and the pages have been of parchment, vellum, papyrus, bamboo slips, palm leaves, silk, wood, and other materials.[from wikipedia]

Natural gas is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, but commonly including varying amounts of other higher alkanes, and sometimes a small percentage of carbon dioxide, nitrogen, hydrogen sulfide, or helium. It is formed when layers of decomposing plant and animal matter are exposed to intense heat and pressure under the surface of the Earth over millions of years.[from wikipedia]

Rock or stone is a natural substance, a solid aggregate of one or more minerals or mineraloids. For example, granite, a common rock, is a combination of the minerals quartz, feldspar and biotite. The Earth's outer solid layer, the lithosphere, is made of rock. Rock has been used by humankind throughout history. The minerals and metals in rocks have been essential to human civilization.[from wikipedia]

A tool is any physical item that can be used to achieve a goal, especially if the item is not consumed in the process. Tool use by humans dates back millions of years, and other animals are also known to employ simple tools. [from wikipedia]